NEW DELHI — Indian officials are advising residents of strife-torn Kashmir to prepare for a possible nuclear war by building bombproof basements and stockpiling food and water, adding to tensions between India and Pakistan, both nuclear powers, after deadly cross-border skirmishes in recent weeks.

“People should construct basements where the whole family can stay for a fortnight,” read the advisory, which was published Monday in the newspaper Greater Kashmir. It comes in the midst of the worst fighting in Kashmir between India and Pakistan since a cease-fire was signed in 2003. Three Pakistani and two Indian soldiers have been killed, and one of the Indian soldiers was found without his head.

News of the mutilation infuriated Indians, with Sushma Swaraj, the leader of the opposition in the lower house of Parliament, calling for India “to get at least 10 heads from their side” if the Pakistanis did not return the soldier’s head. Following criticism that he was not doing enough, India Prime Minister Manmohan Singh said he was reviewing ties with Pakistan. A special visa program between the two countries has been suspended, and Pakistani players in a new Indian field hockey league have been sent home.

Even after both governments embarked on efforts to improve ties after decades of war and recriminations, Kashmir remains a contentious subject. India, heavily Hindu, controls the bulk of the predominately Muslim region of Kashmir, which has been at the heart of disputes between the two nations since they won independence from Britain in 1947. The land along the cease-fire Line of Control is one of the most heavily militarized areas in the world.

The latest clashes started when an elderly woman on the Indian side decided to use a secret entrance into Pakistani territory so that she could see her children living on the other side, according to a report in The Hindu, an Indian newspaper. After the Indian military discovered the tunnel, it built emplacements to prevent its use.

But those emplacements violated the terms of the cease-fire with Pakistan, and Pakistani soldiers repeatedly warned their Indian counterparts to desist, which the Indians ignored.

Firing weapons across the cease-fire line is not unusual, but the beheading, which the Pakistan government denies responsibility for, added a volatile mix to the charged debate. Previous mutilations of soldiers’ bodies have generally been kept secret to avoid just the sort of media firestorm that has erupted.